Q: What is the molar solubility of $$\mathrm{$$PbI_2$$} in $$pure water if $$K_{sp} = 1.20 \times 10$$^{-8}$$?

$$1.2 \times 10$$^{-3}$$\ \mathrm{M}$$

Question 1

What is the oxidation number of phosphorus in $$\mathrm{H_3PO_4}$$?

Accepted Answer

$$+5$$

Question 2

Balance the following redox reaction in acidic solution: $$\mathrm{Cu + $$ClO_3$$^- \rightarrow Cu$$^{2+}$$ + Cl_2$}. $$Which is the correct number of electrons transferred?

Accepted Answer

$$6$$

Question 3

A current of $$0.300\ \mathrm{A} is $$applied for $$40.0$$ minutes to a solution containing $$\mathrm{Au$$^{3+}$$}$$ ions. What mass of gold is deposited? (F = $$9.65 	imes 10^4$\ \mathrm{C/mol\ e^-}$$, Au molar mass = $$197\ \mathrm{g/mol})$$

Accepted Answer

$$2.46\ \mathrm{g}$$

Question 4

Given the cell notation $$\mathrm{Mg(s)\ |\ Mg$$^{2+}$$(aq)\ ||\ Pt$$^{2+}$$(aq)\ |\ Pt(s)}$$, which species is oxidized in the spontaneous galvanic cell?

Accepted Answer

Mg(s)

Question 5

Calculate the cell potential for the reaction $$\mathrm{Al(s) + 3Ag^+(aq) \rightarrow Al$$^{3+}$$(aq) + 3Ag(s)} at$$ $$25^\circ\mathrm{C}$$, given $$E^\circ_{cell} = 2.46\ \mathrm{V}$$, $$[Al$$^{3+}$$] = 1.89\ \mathrm{M}$$, $$[Ag^+] = 0.0850\ \mathrm{M}.$$

Accepted Answer

$$2.36\ \mathrm{V}$$

Question 6

For the reaction $$\mathrm{A$$^{2+}$$(aq) + 2B(s) \rightarrow A(s) + 2B^+(aq)}$$ with $$E^\circ_{red}(A$$^{2+}$$) = 0.77\ \mathrm{V}$$ and $$E^\circ_{red}(B^+) = -0.40\ \mathrm{V}$$, what is the standard free energy change $$\Delta G^\circ in kJ$$?

Accepted Answer

$$-112.6\ \mathrm{kJ}$$

Question 7

What is the molar solubility of $$\mathrm{$$PbI_2$$} in $$pure water if $$K_{sp} = 1.20 	imes 10$$^{-8}$$?

Accepted Answer

$$1.2 	imes 10$$^{-3}$$\ \mathrm{M}$$

Question 8

If the concentration of $$\mathrm{Ag^+} in a $$solution containing $$\mathrm{Ag_2SO_4} is$$ $$4.1 	imes 10$$^{-3}$$\ \mathrm{M}$$ and $$K_{sp} = 1.2 	imes 10$$^{-5}$$, will a precipitate form?

Accepted Answer

Yes, because $$Q \u003e K_{sp}$$

Question 9

Which salt is more soluble in water: $$\mathrm{Mg(OH)_2} or$$ $$\mathrm{Mg(OH)_2} in$$ $$\mathrm{NaOH}$$?

Accepted Answer

$$\mathrm{Mg(OH)_2} in $$water

Question 10

20.0 mL of $$0.100\ \mathrm{M}$$ acetic acid is titrated with $$0.120\ \mathrm{M}$$ NaOH. What is the pH after $$5.0\ \mathrm{mL} of $$base have been added? ($$K_a = 1.80 	imes 10$$^{-5}$$)

Accepted Answer

$$4.74$$

Question 11

For the equilibrium $$\mathrm{H_2$(g) + I_2$(g) \rightleftharpoons 2HI(g)}$$ with $$K_c = 0.150 at$$ $$350\ \mathrm{K}$$, what is the equilibrium concentration of HI if $$0.120$$ moles of $$\mathrm{H_2$}$$ and $$\mathrm{I_2$}$$ are introduced into a $$1.00\ \mathrm{L}$$ vessel?

Accepted Answer

$$0.184\ \mathrm{M}$$

Question 12

For a first order reaction $$2\mathrm{NO_2$} ightarrow \mathrm{N_2O_4}$$ with $$k = 3.31 	imes 10$$^{-4}$$\ \mathrm{s}^{-1}$$ and initial $$[\mathrm{NO_2$}] = 0.400\ \mathrm{M}$$, what is $$[\mathrm{NO_2$}]$$ after $$25$$ minutes?

Accepted Answer

$$0.329\ \mathrm{M}$$

Question 13

A solution is $$10.4\% by $$mass solute (molar mass $$= 58.7\ \mathrm{g/mol}$$), density $$= 1.12\ \mathrm{g/mL}. $$What is the molarity?

Accepted Answer

$$1.99\ \mathrm{M}$$

Question 14

For a process with $$\Delta H = -42.3\ \mathrm{kJ/mol}$$ and $$\Delta S = 8.60\ \mathrm{J/mol\ K} at$$ $$40^\circ\mathrm{C}$$, what is $$\Delta G$$?

Accepted Answer

$$-45.7\ \mathrm{kJ/mol}$$

Question 15

What is the pH of a buffer composed of $$0.120\ \mathrm{M}$$ hydrofluoric acid and $$0.150\ \mathrm{M}$$ potassium fluoride? ($$K_a = 6.80 	imes 10$$^{-4}$$)

Accepted Answer

$$3.22$$

Question 16

After adding $$0.0500$$ mole of HCl to $$1\ \mathrm{L} of a $$buffer composed of $$0.120\ \mathrm{M} HF $$and $$0.150\ \mathrm{M} KF$$, what is the new pH?

Accepted Answer

$$2.70$$

Question 17

Given the following initial rates for $$2\mathrm{NO}(g) + \mathrm{Cl_2$}(g) \rightarrow 2\mathrm{NOCl}(g)$$, what is the rate law?

Accepted Answer

Rate $$= k[\mathrm{NO}]^2[\mathrm{Cl_2$}]$$

Question 18

For the equilibrium $$2\mathrm{A}(g) ightleftharpoons 2\mathrm{B}(g) + \mathrm{C_2$}(g)$$ with $$K_c = 5.87 	imes 10$$^{-3}$$ at 279$$\ \mathrm{K}$$, what is K_c$ for $$\mathrm{A}(g) ightleftharpoons \mathrm{B}(g) + \frac{1}{2}\mathrm{$$C_2$$}(g)$$?

Accepted Answer

$$7.66 	imes 10$$^{-2}$$

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